New power lines are to be laid across the Norfolk Broads, one of Britain’s
finest scenic areas, to serve offshore windfarms.

Documents published by National Grid show a new 25-mile cable line will be built from Lowestoft to Norwich, cutting through the popular holiday spot.

The lines are needed to connect the national network to a vast new windfarm, one of the biggest in the world, under construction off the Norfolk coast.

The cables could still be buried, but if they are not, more than a hundred pylons, each the height of a 15-storey building, would run alongside, or parallel to, the River Yare, dominating the Broads for miles around.

They would also affect the lower reaches of another celebrated Broads river, the Waveney, and possibly also Oulton Broad.

Another possibility is to route them further south, along the Waveney and past the town of Beccles, to join the existing electricity grid near the town of Diss.

This stretch of the Waveney is also part of the Broads. The southern route is not shown in the National Grid documents, however.

“My understanding is that there are two options, either down the Waveney Valley or the Yare Valley,” said the leader of South Norfolk District Council, John Fuller.

“We understand it could be above ground or below ground, and we are making it absolutely clear that the only acceptable solution is below ground, because of the effects on the Broads.”

Guy McGregor, Suffolk County Council’s cabinet member for transport and a member of the Broads Authority, said the proposals were “staggering".

He added: “The Broads is a national park in everything but name. We’ve been spending a lot of effort getting distributor cables [smaller power lines] underground. There is no way we could countenance pylons here — it would be quite devastating.”

The new line is revealed in the latest edition of a National Grid document, Transmission Networks Quarterly Connections Update, on the company’s website, with a line on a map showing “new-build” lines between Lowestoft and Norwich.

A National Grid spokesman said that more details of the scheme would be given in the New Year. “The line on the map is just a guide at this stage for the sort of area it needs to be in,” he said.

“Next year a full options report will be published and we will start consulting people and asking them what they think.”

The proposal arises from the East Anglia Offshore Wind Project, a scheme which could involve as many as 325 turbines at sea with a capacity for 1.2 gigawatts of electricity. The actual amount generated will be much less, but still substantial.

The windfarm is divided into seven zones. Electricity from the first zones to be built will come ashore at Bardsey, on the southern Suffolk coast. Underground cables will then take it to Bramford, on the outskirts of Ipswich.

Even this has proved highly controversial, since it will require a new above-ground pylon line through Constable country from Bramford to Twinstead, in Essex, en route to consumers in London. Locals have mounted strong opposition to the scheme.

However, electricity from later phases of the windfarm will come ashore at Lowestoft. The only way to get it to from here to the electricity grid, which runs roughly parallel to the main railway line between Norwich and Ipswich, is to go through the Broads.

A spokesman for Scottish Power Renewables, which is building the windfarm, said: “The first connection agreements [into the grid] we would be looking for would be into Bramford. Beyond that, National Grid have given us connection agreements at Lowestoft and Norwich.” However, he said that this would not happen until after 2016.

“Where you’ve got big horizons, as in the Broads, tall structures are far more intrusive than they would be in an undulating landscape,” said David Hook, of the Norfolk branch of the Campaign to Protect Rural England.

“Even though it is offshore wind, there is an enormous potential impact on the landscape from the infrastructure associated with it.”

In June, The Telegraph revealed that hundreds of miles of new pylon lines would be needed in many scenic areas to serve windfarms, which are typically more dispersed and further from main population centres than traditional power stations.

The cables are often proving more controversial than the turbines themselves and their cost is weakening the economics of wind power.

Tourism is the Broads’ main industry, with around seven million visitors spending £400 million a year and supporting 10 boatyards on the Yare between Norwich and Reedham alone.

Wind projects have already hit other parts of Norfolk, with parts of the county’s famous northern coast blighted by windfarms within sight of the shore.

James Knight, owner of the Waveney River Centre, near the course of both proposed routes, said: “We look out at a clear view as far as the eye can see.

"It’s one of the things we’re selling. If there was a whole bunch of pylons marching across in front of our business, that would clearly have an impact.”